Apparatus for telephone-switchboards.



PATENTED APR; 3,-1906. H. E. A. ANDRE.

APPARATUS FOR TELEPHONE SWITCHBOARDS. APPLIOATION gum) APR. 27, 1904.

WIT/VL'SEEF.

a? T TUNA/51%.

HENRI EMILE s'iLIIlONE-IE ANDRE, ()I PARIS, FRANCE, ASSIGNOR TO FERN lfilil lt 'lltltl COMPANY, OF (Il-llCAGO. ILLINOIS, A CORPO- N0. nicest.

Specification of Letters Patent.

'ratentecl April 3, 1906.

Application filed April 27, 1904. Serial No. 205,089;

To (Ml iv/1 0717 it may concern; 1

Be it known that I, HENRI EM ILEALPHONS a ANDRE, a citizen of France, residing at Paris, France, have invented a certain new and useful Improvement in Apparatus for 'lelepbonc- Ewitchboa-rds, oi' which the following is a lull, clear, concise, and exact descrhition.

My invention relates to a central-utilize apparatus for telephone-ext;hangcs; and its object is to insure secrecy in telephonic communication between subscribers by preventing 1 the operator from listening in on a busy circuit.

The principal feature of the invention is a blocking device adapted to render the centraloflice telephone apparatus inoperative--as, for example, a cut-otl switch or a switch to apply a characteristic tone-producing current, or both--and means actuated in the act of making con nection witlta busy line for operating the aforesaid blocking device. The telephone may also be out off by the act oi completing a connection from a calling to a called line.

I will describe the invention particularly by reference to the accompanying drawing, which is a diagram illustrating two subscribers lines extending from substations to a central ollice with the operatons plug-circuit apparatus for commuting lines together, the systen'i being equipped with my improved blocking mechanism 'l'or insuring secrecy.

In accordance with the inultiple-switchi board system each line is provided with several multiple connection terminals or springjacks, at any one of which connection may be made with the line. A pair oi plugs a I), united by the link coruluctors l 2 of a plugcircuit, is illustrated, whereby any two lines may be looped together for conversation. The plugs illustrated are ordinary three-part plugs, each of which has tip, ring, and sleeve contacts a a (15 b b b, these three contacts being adapted to engage the short and long line-springs and the test-ring, respectively, of any spring jack into which the plug may be inserted. The tip and ring contacts of each plug form the terminals of the link eonduc' tors 1 and i respectively, and the third con tact of each plug forms the terminal of a )ortion of a local circuit from a grounded iattery e, which is adapted to be closed by the insertion of the plug in any spi'ingjack, the,

' winding f'" circuit being completed by a conductor 5, associatcd with the cci'itral-ollice apparatus of the line to which connection is made. The cmnluctor 5 ol' any line extends from the testrings oi the -scvcral multiple spring-jacks of such line through a "rcstoriiig-winding d of the clcctromagnctic line-signal (I to earth. Such conductors 5 from the test-rings oi the jacks for completing a local circuit when any jack is plugged into are well known in the art. I

The portion of the local circuit from battcry c, which is adapted to be completed by the answcrii'ig-plng a, is designated in the drawing by the reference-ligure 3, and the portion oi the othcr'local circuit to the calling-plug is designated as 4. The conductor 3 includes the helix of a relay-magnet e, and the conductor 4 includes one of the two helices f of an clectromagnetic switch which controls the cormection of the centralolliee telephone g with the. plug-circuit. The switchfconstitutes a blocking device for rendering the tclta'ihonc apparatus inoperative by, cutting it oil from the plug-circuit. The switch has two lovers connected, respectively, with the limbs 1 2 of the plug-circuitand normally resting against back-contact anvils which form the terminals of the operators telephone apparatus. When either of the windings f receives current, these two switch-levers will be lifted from their back contacts, thus cutting oil the telephone. The is included in. a local circuit 6 from the battery 0, which circuit also includes the inagl'ict-winding of a relay l1 and one winding? of a relay 1' and is controlled by the armature and front contact of the said relay i and also by the spring and its resting contact-anvil of a plug-start switch A'. The switch /r is normally opened by the presence oi the answciting-plug n in its socket, but automatically closes itself when the plug is removed. The other winding '5 of the relay i is included in a ground branch 7 from the tip-strand l of the plug-circuit and is controlled by the relay c. This ground branch 7 is normally closed at the armature and back contact of the relay but is broken when said relay is excited.

The middle point oi the winding of the centrahollico operatoi"s telephone is connected to earth, and a local branch 8 to earth from the telephoncadre-nit, including the secondary winding of an induction-coil Z, is adapted to be closed by the relay h when excited, whereby a characteristic signal produced at the induction-coil may be applied to the operators telephone. To produce such a signal, the primary winding of the induction-coil may be included in a circuit with-a source of current and an interrupter, as shown. hen the relay it is excited, therefore, a buzzer hum is produced in the telephone. The plugs and jacks are so constructed that it will be impossible 'to insert a plug in a jack without establishing at least for a moment a contact between the ring of the jack and the tip of the phone.

.of relay i.

plug. This may be accomplished by making the tip of the plug ot'a size so that it will barely slip through the test-ring. The distance between the tip and third contact of the plug should also be sutlicient to prevent the test-ring from short-circuiting the two as the plug is being inserted.

The operation of the system may be traced as follows: When a call is received at the central ollice, the operator responds by inserting her answering-plug (1 in the spring-jack of the calling-line. The circuit 3 is completed and relay c d 'aws up its armature, thus cutting oil the b 'anch T,whieh includes the windingi (ircuit (i being open at the contacts of relay '1', the electromagnetic switch orv blockingdevice f remains inert, so that the telephone 9 may be used to ascertain the number of the subscriber with whom connection is desired. When this information is obtained, the operator may then test the springjackof the line wantedwith the tip of the calling-plug in the usual manner, and it the line is free she may complete the connection by inserting the alling-plug into the spring-jack. The insertion of the callingplug completes the circuit 4 and excites the magnetf, thus cutting oil the operator's telelt is understood, oi" course, that each operator at ac-h section of the multiple switchboard is provided with a number ot pairs of plugs with their associated apparatus and circuits, such as shown in the drawing, a single pair only being illustrated for clearness. Whenever a plug is inserted in any of the multiple spring-jaeks of a line, the test-rings ot'all the spring-jacks, bcingunited by the conductor 5, are electrified or given a test potential, the battery being applied to the test-ring oi the jack in which the plug is in serted by way of the conductor, which terminates in the third contact or sleeve of the plug. it the operator should attempt to listen in on a busy line with the answeringplug of an idle pair in inserting the plug into the spring-jack of the line, the tip of the plug would to'uch the ring-contact ot' the jack as it was, being inserted. Since a. connection already, existed at another of the multiple jacks, there would be a ditl'erence of potential between the ring of the jack and the plug-tip,

' and current would flow through conductor 7. energizing the relay 2'. In drawing up its ar- 5 mature the relay i closes the circuit 6, which includes the windings of relays f and h, and also a locking-winding i of its own magnet. Relays f and it thus become excited, cutting off the operators telephone g from the cordcircuit and at the same time applying to said telephone the current from the induction-coil I, which produces a disagreeable buzz or hum. Since the circuit 6 includes the locking-winding 4?, the answering-plug must be replaced in its socket in order to break the circuit and stop the noise in the telephone.

1t is evident that my invention is capable of modification and I do not desire to be understood as limiting myself to the precise cir cuits and apparatus shown; but,

llaving described one embodiment of my invention, I claim 1. The combination with a number of telephone-lines each provided with multiple connection-terminals at a central switchboard,

conductor connecting said plugs for uni-ting any two of said lilies at the connection-terminals thereof, a central-office telephone apparatus adapted to'be connected with said link conductor, a local circuit setablished in the act of making connection from either plug to the terminal of any busy line, a relay in said local circuit, blocking mechanism controlled by saidrelay for rendering the central-office telephone apparatus inoperative for communication over said link conductor, and means actuated in making connection with any line for establishing at the several multiple terdition to which the said relay is responsive when the circuit of said relay is established at another multiple terminal ot the same line. whereby the central-office telephone apparatus is automatically blocked when it is attempted to make connection with a busy line.

2. The combination with a number of telephone-lines each provided with multiple connection-terminals at a central switchboard, of

lines at/t' 'he connection-terminals thereof, a central-oilice telephone adapted to be connected with said link conductor, a local circuit established in making connection from the link conductor to the terminal of any busy line,a relay in said local circuit, a source of signal-current adapted to produce a characteristic sound in the telephone, switching mechanism controlled by said relay adapted to apply said source of signal-current to the controlled by saii relay for rendering the central-otlice telephone inoperative fol-communi- 'cation over said link conductor, and means actuated in making connection with a multiple terminal of any line for establishing at the other multiple terminals a peculiar electrical minals of such line a peculiar electrical con-' a link conductor for uniting any two of said central-otiice telephone, blocking mechanism.

of an answering and a calling plug, a link tor when a plug 8. The combination with multiple springjack line-terminals at a-telephone-switchboard, and a test-conductor uniting the respective test-contacts of said spring-jacks, pin s and plugcircuits, means associated with each plug adapted to establish a pcculiar electrical condition of said test conducis inserted in any of said spring-jacks, a telephone normally associated with each plug-circuit, a branch from one'of the talking-strands of eachplug-circuit, saidbranch being adaptedto be momentarily brought into connection with the said test-conductor during the insertion of the plug associated therewithinto a spring-jack, a relay in eachbranch adapted to respond to such changed electrical condition of said test conductor, a' source of signal current adapted to produce a characteristic tone in said telephone, and switching mechanism controlled by said relay adapted to sever the con- =nection of said telephone with the p ug-circuit and connect the same with said source of signal-current.

9. The combination with a plug and plugcircuit, of telephone apparatus adapted for connection with said plug-circuit, an electromagnetic switch adapt-ed to render said tele phone apparatus inoperative during connection, an actuating-circuit for said switch t rminating on a test-contact of the answeringplug, a telephone-line, a spring-jack terminal therefor, a part of said Spring-ja0k adapted to be engaged tact of the plug as the plug is inserted in making connection with the line, and a source of current adapted to be applied to said part in the use of the telephonc line, whereby said electromagnetic switch is actuated to render the telephone inoperative when connection is made with a line which is in use.

10. The combination with a number of telephone-lincs extending from substations to multiple terminals at a central office, of an answering and a calling plug, and a plugcircuit therefor for uniting said lines, telephonic ap aratus associated with said plugcircuit, b ocl ing mechanism for rendering said telephonic apparatus inert, a relay-for operating said blocking mechanism, and a circuit for said relay swering-plug engages hne.

In Witness whereof I hereunto subscribe my name this 7th day of March, A. D. 1904.

HENRI EMILE ALPHONSE ANDRE.

the terminal of a busy W'itnesses HANsoN 0. (learn,

JOHN BAKER.

momentarily by the test-concompleted as said an- 

